Unalligned access in Mod_LoadMarksurfaces

[andrey-budko]

I noticed that Mod_LoadMarksurfaces can potentially perform an unaligned access. See this comment for details:
andrei-drexler#570 (comment)

Corresponding part of the code

short *in = (short *)(mod_base + l->fileofs);
if ((uintptr_t)in & 1)
    __debugbreak();

As far as I understand, this is UB (at least), and I tried to port Novum's fix Novum/vkQuake@c1b0234 in case you're interested.

andrey-budko@f61f19f

I did all the changes by hand, so be careful and recheck it in case you are interested in such huge changes. Most changes are fairly trivial, but Mod_LoadTextures required extra care as the code differs significantly.

[lndpj]

Multiple threads might access the in array at the non-power 2 address in background during model caching causing a race condition. Using a mutex lock or semaphore might be a solution.